Pressurized toilet cistern

ABSTRACT

A toilet-flushing ( 1 ) device comprises a container ( 2 ) divided by an elastic diaphragm ( 3 ) with a direct unrestricted connection to a water supply under pressure at the lower part of the container ( 2 ), with a flushing valve ( 15 ) also in the lower part of the container. The water distends the diaphragm ( 3 ) so that when the flushing valve ( 15 ) is opened, the diaphragm ( 3 ) ejects the flushing water fast, allowing a small volume flush to effectively clear the toilet trap ( 2 ) and sewer. Extension of the diaphragm can be reduced by having two diaphragms ( 55 ), ( 56 ), each providing half the flush volume by their extension. Substantial water saving is enabled. A water pressure actuated valve ( 35 ) that is well adapted for application to this device is disclosed.

FIELD OF THE INVENTION

The present invention lies in the field of toilet flushing.

BACKGROUND

Existing toilet cisterns make use of a float valve to control the flowof water into a cistern, from which the water is flushed into toiletbowl under action of gravity on the water in the cistern. A lot of wateris required with this system to clear the toilet trap and sewer, between9 and 13 litres of water are typical. If water can be saved per flush,millions of litres can be saved on a daily basis in many countries ofthe world.

The inflow of water into a cistern is controlled by a float valve, theresult is that it takes quite a while for the cistern to be filled andto be ready for the next flush. This results in public toilets in thebowl often being dirty as the toilet is not ready for the next flushquickly enough.

Because the float valve progressively restricts the inflow of water asthe cistern approaches full, a considerable noise is associated with thefilling. This noise is particularly objected to in domesticinstallation.

These three problems with toilet cisterns are in need of a solution.

Time delay valves have been used to flush a toilet bowl, but are not acompletely satisfactory solution. The valves limit the flow rate of theflush so that again a lot of water is required to clear the trap andsewer. They have been used more successfully in urinals. The valves alsotend to be unreliable.

A design has been proposed that uses an electrically motorised pump toproduce the flush that it claims is a powerful and quiet action, with adual flush option. Whether these claims are met or not is uncertain, butthe device has undoubted technical complexity and resulting cost and theundesirable combination of electricity and water, in a domestic orpersonal use appliance.

The term “toilet” used herein refers to the fixture used to defecate orurinate and having a means of flushing.

There is a need to find a better flushing means.

THE INVENTION

A toilet-flushing device in accordance with the present inventioncomprises a container for toilet flushing water that is partiallyenclosed by an elastic membrane or diaphragm and partially by a rigidwall that has an unrestricted connection to a source of water underpressure that is sufficient to extend the membrane and an outlet for aflushing valve operable to release water from the container for a flushof a toilet bowl or urinal.

Preferably the device has a retaining structure to support the diaphragmagainst excessive extension that could lead to it bursting. Although theretaining structure could be a grid or mesh, it is preferable that it isan in-perforate rigid wall like the wall that has the connection andflushing valve referred to, but with an aperture to allow air to move ina and out as the membrane expands and contracts, in use.

The inlet for water under pressure can be a spigot that is always open,though if desired a non-return valve can be fitted to prevent backflowinto the supply pipes. The water under pressure can typically besupplied by municipal mains water under the ordinarily availablepressure, or a regulated pressure can be used.

A design has been proposed that uses an electrically motorised pump toproduce the flush that it claims is a powerful and quiet action, with adual flush option. Whether these claims are met or not is uncertain, butthe device has undoubted technical complexity and resulting cost and theundesirable combination of electricity and water, in a domestic orpersonal use appliance.

Toilet flushing mechanisms with an elastic tubular membrane, disc-shapeddiaphragm or bag, that accelerates the flush have been proposed, but ithas become clear that it is desirable to limit the extent to which thediaphragm or membrane is distended. For example, GermanOffenlegungschrift 1 908 970 (1969) discloses an elastic tube (elasticheBlase) located in a retaining structure (Behälter) with an inlet(Zulaufrohr) and flushing outlet (Ablaufrohr) controlled by a valve(Verschluss). U.S. Pat. No. 4,115,883 (1978) discloses a singledisc-shaped diaphragm (24) in a retaining structure (22,30) withflushing outlet controlled by a valve (34). French patent 1 128 196 Adiscloses a toilet flushing device that comprises a container for toiletflushing water (vessie en caoutchouc 5) that is partially enclosed by abag-shaped elastic membrane (vessie 5) and partially by a rigid wall(plaque 9) that has an unrestricted connection to a source of waterunder pressure that is sufficient to extend the. membrane (tube 10) andan outlet in the rigid wall for a flushing valve operable to releasewater from the container for a flush of a toilet bowl or a urinal (canal11) with a retaining structure (réservoir 1) to support the diaphragmagainst excessive extension that could lead to it bursting (réservoir 1)with an aperture to allow air to move in and out as the membrane expandsand contracts, in use.

In these designs it is not possible to limit the distension in aflushing mechanism of acceptable size and it is not possible tocompactly locate the flushing valve and control rod inside.

The term “toilet” used herein refers to the fixture used to defecate orurinate and having a means of flushing.

There is a need to find a better flushing means based on a solution tothe technical problem of defining an alternative structure that useselastic diaphragms or membranes while limiting the extent to which thediaphragm or membrane is distended and making it possible to locate theflushing valve inside the flushing means.

THE INVENTION

A toilet-flushing device in accordance with the present inventionincludes a container for toilet flushing water that is partiallyenclosed by an elastic membrane or diaphragm and partially by a rigidwall that has an unrestricted connection to a source of water underpressure that is sufficient to extend the membrane and an outlet in therigid wall for a flushing valve operable to release water from thecontainer for a flush of a toilet bowl or urinal, with a retainingstructure to support the diaphragm against excessive extension thatcould lead to it bursting, the retaining structure being a rigid walllike the wall that has the connection and flushing valve, but with anaperture to allow air to move in and out as the membrane expands andcontracts, in use, characterised in that a structure is defined by whichthe container for toilet flushing water is partially enclosed by twodisc-shaped elastic membranes or diaphragms and partially by the rigidwall, which is cylindrical in shape and extends between the peripheriesof the two diaphragms, the wall having an unrestricted connection to asource of water under pressure that is sufficient to extend the twomembranes and the outlet for a flushing valve located in the spacedefined by the cylindrical wall, operable to release water from thecontainer for a flush of a toilet bowl or urinal.

The device as mentioned has a retaining structure to support thediaphragm against excessive extension that could lead to it bursting.Although the retaining structure could be a grid or mesh, it ispreferable that it is an in-perforate rigid wall like the wall that hasthe connection and flushing valve referred to, but with an aperture toallow air to move in a and out as the membrane expands and contracts, inuse.

The inlet for water under pressure can be a spigot that is always open,though if desired a non-return valve can be fitted to prevent backflowinto the supply pipes. The water under pressure can typically besupplied by municipal mains water under the ordinarily availablepressure, or a regulated pressure can be used.

The way that the invention works, is that the water under pressure fillsthe container, distending the diaphragm. Because the inlet isunrestricted, the filling is quick and silent. The distension of thediaphragm stores energy in the diaphragm, which is released when theflushing valve is opened, as the diaphragm ejects the water forcibly inthe flush This provides a higher rate of flushing than is usual, whichallows a smaller quantity of water to be effective in clearing the trapand sewer. The fact that the inlet for water under pressure remains opendoes not cause any untoward effect, as the pressure in the containerdrops the moment the flushing valve is opened so that there is nobackflow of water into the supply system (that would be objected to byauthorities) and a small inflow does not have any undesired effect

The characterising feature of the invention comprises what could becalled a “tandem” arrangement of diaphragms, namely the container fortoilet flushing water is partially enclosed by two elastic membranes ordiaphragms and partially by a rigid wall between the two diaphragms thewall having an unrestricted connection to a source of water underpressure that is sufficient to extend the membranes and an outlet for aflushing valve operable to release water from the container for a flushof a toilet bowl or urinal.

Both membranes preferably have retaining structure, preferably in theform of walls on the outer side of the diaphragms.

An optional feature is to provide a connection from the space on theside of the diaphragm opposite to the space holding the flushing water,that is the enclosed space leading to the trap. The effect achieved bythis connection, is that when the flushing valve is opened and thediaphragm relaxes, it draws air from the trap into the space above thediaphragm, this reduces the pressure in the trap and enhances the rateof flush into the trap.

The trap is the space adjoining the toilet bowl to which is connectedthe soil pipes to the sewer, and is isolated from the bowl by the waterlevel in all toilet bowls, to prevent unpleasant odours from the sewerflowing back.

The invention may also be implemented by means of a spring-loaded pistonor pistons in a cylinder or cylinders, instead of the diaphragm(s). Thepiston will be pressed back along the cylinder, analogously to thediaphragm distending, the spring providing the elastic response that theelasticity of the diaphragm, which is e.g. of rubber, provides. In bothcases the incoming water from the pressurised mains supply builds uppotential energy, in the diaphragm in the elastic distension, and in apiston in the spring. energy as the spring is tensioned. This energyprovides the strong flush that allows use of less water.

The flush valve may be selected from suitable valves available, as wellas the means of opening and closing it, for a flush. A large opening issought after and, for example, pressure balanced valves and pressureactuated valves, which balance pressure generated forces or give aservo-type enhancement to allow a light mechanical control, can be agood choice. The present invention provides a design of valve that iswell adapted to use with the invention.

According to a preferred embodiment, the toilet-flushing device of theinvention further includes a flushing valve connected to the flushingoutlet of the container, which valve comprises a valve seat, a diaphragmincluding a plug that can seat on the valve seat, a wall joining withthe diaphragm to enclose a space within the diaphragm and wall, anaperture in the plug upstream of the valve seat, a control aperture inthe wall downstream of the seat, that can be closed and opened by acontrol means operable by a. user of the toilet-flushing device.

This valve uses the pressure of the water in the container to move thevalve plug from open to closed and closed to open. This allows controlof the valve for flushing to be effective and easy over a range of waterpressures, e.g. as may occur from different municipalities and differinglocations in a municipal system.

The device preferably has a valve of a type that will close if thediaphragm develops a leak or bursts, to ensure that there will be nowater leakage in that event. The valve can, for example, be a ball thatis lifted to a closed position by water but not by air, so that thevalve allows the air to move freely in and out of a space between thediaphragm and the retaining structure wall.

THE DRAWINGS

The invention will be more fully described by way of examples, withreference to the drawings, in which:-

FIG. 1 is an isometric view of a toilet-flushing device not according toan embodiment of the invention, sectioned in half for illustrationpurposes,

FIG. 2 is an isometric view of the device,

FIG. 3 is a schematic drawing of a sectioned view of an installation ofthe device on a toilet bowl,

FIG. 4A is a sectioned view of a flushing valve provided as a preferredfeature of the invention, in a closed position,

FIG. 4B is a sectioned view of the flushing valve, in an open position,

FIG. 5 is a sectioned view of a device according to the preferredembodiment of the invention, and

FIG. 6 a sectioned elevation of the preferred device

THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 are not according to the invention, this toilet-flushingdevice 1 comprises a container 2 for toilet flushing water that ispartially enclosed by an elastic membrane or diaphragm 3 and partiallyby a rigid wall 4 that has an open spigot 5 for unrestricted connectionto a source of water under pressure that is sufficient to extend themembrane and an outlet 6 for a flushing valve operable to release waterfrom the container for a flush of a toilet bowl or urinal.

The device has a retaining structure to support the diaphragm againstexcessive extension that could lead to it bursting, in the form of arigid wall 7 like the wall that has the connection and flushing valvereferred to, but with an aperture 8 to allow air to move in a and out asthe membrane expands and contracts, in use. A ball can be put in thespace 53 above the diaphragm so that if the diaphragm should perish andbreak the ball will be driven into the hole 8 to close it and preventflooding.

The two walls 4 and 7 have flanges 9 and 10 respectively that are boltedtogether, clamping the diaphragm between them. Though shown as of equaldimensions, the top wall 7 does not have to be the same size as thebottom wall 4. Bolts are used at the flanges to clamp them together. Thewalls 4 and 7 thus form a container divided by the diaphragm 3.

The inlet is threaded at 11 and the outlet is threaded at 12, forappropriate connections.

FIG. 3 shows the device 1 connected with a toilet bowl 13 and amunicipal water supply 14, for use. The same reference numerals are usedfor the device as were used in FIGS. 1 and 2. The invention can beapplied to this installation.

The device has a flushing valve 15 attached to it, communicating withthe flushing passages 16 of the toilet bowl. The flushing valve has aconnection 17 to a manual actuator 18 mounted in a partition or wall 19that hides the container from sight. The toilet bowl has water in it at20, providing the odour seal from the trap 21. The trap is connected tothe soil pipes 22 and sewer by a connector 23. A flap valve 24 is shown,being an optional feature.

A pipe 25 connects from a fitting 26 in the connector to a fitting 27applied to the aperture 8 at the top of the container. The pipe providescommunication from the space 53 above the diaphragm 3 to the space inthe trap 21.

The inlet pipe 14 has a stop-cock 29 that is normally kept open and onlyused to isolate water supply under pressure if the container must bedisconnected for servicing.

The container holds six litres of water for the flush, when thediaphragm is in the position indicated by the broken lines 30, havingbeen distended to that position by the water under pressure entering viathe spigot 5. The quantity of 3 litres compares very favourably with 9to 12 litres typical in toilet cisterns, leading to potential for watersaving of millions of litres in large cities and in countries at large.Given a typical cost of water, enormous savings in monetary terms areattainable. As mentioned because the spigot allows unrestricted flowinto the container the time to fill it is less than in the case of afloat controlled cistern and the filling is silent. The device is thenready for a flush.

When the flushing valve is actuated, the tension in the diaphragm expelsthe water from the container at higher speed than occurs in the case ofa typical gravity actuated flush from a toilet cistern. This is whatallows the flush to be effective in clearing the trap and downstream thesewer.

Specifications have been developed by the South African Bureau ofStandards (SABS), which is an accredited standards authority with theinternational bureau of standards authorities. This standard, under SABS1733:1998 for water closet (toilet bowl) flushing systems requires theuse of 50 balls produced form a non-absorbent, durable material, ofdiameter 19.0 mm and of a relative density between 0.85 and 0.88, in aprescribed test procedure. The 50 balls are placed in the toilet bowl,filled to its normal level. The bowl is then flushed with one full flushand the number x of balls that remain in the bowl is recorded. Thestandard then allows for up to three more flushes to empty the trap ofall balls, the number y of additional flushes required is recorded. Thefollowing formula is used to get to a number R:R=100−2x−7y ²

R must be more than 60 for a flushing system to conform to standard. Aprototype of this invention made according to this embodiment scored 93for R.

The device is smaller than a cistern and can be made in a prolatespheroidal or other shape rather than a spherical shape, for example, tomake it even more space saving. The device lends itself to attachment oreven integral manufacture with the toilet bowl, due to its compactness.

Typical water supply pressures that are met with range between 2 bar and6 bar (between 200 kPa and 600 kPa). If desired, the inlet can be givena pressure regulator valve provided that it is of a design that will notrestrict the rate of inflow into the container, however, a better optionis to use a suitable valve that does not require a controlled pressure.

FIGS. 4A and 4B show a valve that has been designed to be used with theinvention.

The valve 35 is connected at inlet 36 to the flushing outlet 6 of thecontainer and at outlet 37 to the flushing passages 16 of the toiletbowl. The valve comprises a valve seat 38, a diaphragm 39 with which isintegrally formed a plug 40 that can seat on the valve seat, a wall 41joining with the diaphragm to enclose a space 42 within the diaphragmand wall. An aperture 43 in the plug upstream of the valve seat, acontrol aperture 44 in the wall downstream of the seat, that can beclosed and opened by a control means 45 operable by a user of thetoilet-flushing device.

When the aperture 44 is closed the water pressure at inlet 36 enters thespace 42 via the aperture 43 and distends the diaphragm moving the pluguntil it seals against the seat 38, as shown in FIG. 4A The water underpressure will then distend the diaphragm 3 in the container 1 (FIG. 3)preparing the device for a flush.

When the aperture 44 is opened the water in the space 42 dischargesthrough the aperture 44 and the diaphragm moves off the seat 38,allowing a flush to take place. The passages 46 are made large enough toallow a fast flush, as indicated by the arrows 47.

The inlet end of the valve is provided with a tapered needle valve 48 toprovide a gradual closing of the valve onto the valve seat, so as toavoid a violent action that could cause damage or water hammer.

The control means 45 comprises a lever 49 pivoted at 50 with a spring 51urging it to close the aperture 44 and a rod or wire (cable) 52 to openit when a flush is required. The valve is thus normally closed and openswhen actuated. The valve could alternatively be electrically operated.

Structural aspects of the design are apparent from the drawing to thetrained eye. Materials can be suitable types and grades of plastics,injection moulded and rubbers for the diaphragms. Design techniques caneasily attain say up to 30 bar (3 mPa) ultimate strength and a safetyrelief valve can be provided.

FIGS. 5 and 6 show the preferred design according to the invention. Ithas become clear that it is desirable to limit the extent to which thediaphragm is distended. Suppliers advise that their particular productbe limited to a maximum distention of 15%.

In order to achieve this, a solution is the design shown in these twofigures, where the total volume flush is provided by two diaphragms,thus halving the degree of distention required of the diaphragm.

Thus the device comprises a container 54 for toilet flushing water thatis partially enclosed by two elastic diaphragms 55 and 56 and partiallyby a rigid wall 57 that has an unrestricted connection 58 to a source ofwater under pressure that is sufficient to extend the membranes and anoutlet 59 for a flushing valve 60 operable to release water from thecontainer for a flush of a toilet bowl or urinal.

The device has a retaining structure 61 and 62 to support the diaphragmsagainst excessive extension that could lead to leaks or bursting. Thevalve 60 is controlled by means of a rod or tube 63, the valve and thecontrol not being described with reference to these figures of thedrawings. The retaining structures are un-perforated walls as shown andhave holes with vents 64 and 65, designed to allow air to move into andout of the spaces 66 and 67 that are behind the diaphragms. The vents,however, each have a small ball valve that will close the vent if waterstarts to issue from the vent, thus preventing flooding if the eitherdiaphragm starts a leak or bursts.

1. A toilet-flushing device, comprising; a container for toilet flushingwater, that is partially enclosed by two disc-shaped elastic membranesand partially by a rigid wall, which is cylindrical in shape and extendsbetween the peripheries of the two membranes, the cylindrical wallhaving an unrestricted connection to a source of water under pressurethat is sufficient to extend the two membranes and an outlet for aflushing valve located in a space defined by the cylindrical walloperable to release water from the container for a flush of a toiletbowl or urinal, a retaining structure to support the membranes againstexcessive extension, the retaining structure being a rigid wall with anaperture to allow air to move in and out as the membrane expands andcontracts, wherein the toilet-flushing device further includes aflushing valve connected to the flushing outlet of the container, whichvalve comprises a valve seat, a diaphragm including a plug that can seaton the valve seat, a wall joining with the diaphragm to enclose a spacewithin the diaphragm and the wall, an aperture in the plug upstream ofthe valve seat, and a control aperture in the wall downstream of theseat, that can be closed and opened by a control means operable by auser of the toilet-flushing device.
 2. A toilet-flushing device,comprising: a container for toilet flushing water; wherein the containeris partially enclosed by an elastic membrane and partially by a rigidwall that has an unrestricted connection to a source of water underpressure that is sufficient to extend the membrane and an outlet in therigid wall for the flushing valve operable to release water from thecontainer for a flush of a toilet bowl or urinal; and a flushing valveconnected to a flushing outlet of the container, which valve comprises avalve seat, a diaphragm including a plug that can seat on the valveseat, a wall joining with the diaphragm to enclose a space within thediaphragm and the wall, an aperture in the plug upstream of the valveseat, and a control aperture in the wall downstream of the seat, thatcan be closed and opened by a control means operable by a user of thetoilet-flushing device.
 3. The toilet flushing device as claimed inclaim 2, wherein the device has a retaining structure to support thediaphragm against excessive extension, the retaining structure being arigid wall with an aperture to allow air to move in and out as themembrane expands and contracts.
 4. The toilet flushing device as claimedin claim 2, wherein the inlet for water under pressure is a spigot thatis always open, save for a non-return valve fitted to prevent backflowinto the supply pipes.
 5. The toilet flushing device as claimed in claim2, wherein a connection from the space above the diaphragm that isenclosed to a trap is provided, so that when the flushing valve isopened and the membrane relaxes, it draws air from the trap into thespace above the membrane and reduces the pressure in the trap andenhances the rate of flush into the trap.
 6. The toilet flushing deviceas claimed in claim 2, wherein the container for toilet flushing wateris partially enclosed by two elastic membranes and partially by a rigidwall between the two membranes.
 7. A toilet-flushing device, comprising;a container for toilet flushing water; wherein the container ispartially enclosed by an elastic membrane and partially by a rigid wallthat has an unrestricted connection to a source of water under pressurethat is sufficient to extend the membrane and an outlet in the rigidwall for the flushing valve operable to release water from the containerfor a flush of a toilet bowl or urinal and a retaining structure tosupport the membrane against excessive extension, the retainingstructure being a rigid wall with an aperture to allow air to move inand out as the membrane expands and contracts, and a flushing valveconnected to the flushing outlet of the container, which valve comprisesa valve seat, a diaphragm including a plug that can seat on the valveseat, a wall joining with the diaphragm to enclose a space within thediaphragm and the wall, an aperture in the plug upstream of the valveseat, and a control aperture in the wall downstream of the seat, thatcan be closed and opened by a control means operable by a user of thetoilet-flushing device.
 8. The toilet flushing device as claimed inclaim 7, wherein the inlet for water under pressure is a spigot that isalways open, save for a non-return valve fitted to prevent backflow intothe supply pipes.
 9. The toilet flushing device as claimed in claim 7,wherein a connection from the space above the diaphragm that is enclosedto a trap is provided, so that when the flushing valve is opened and themembrane relaxes, it draws air from the trap into the space above themembrane and reduces the pressure in the trap and enhances the rate offlush into the trap.
 10. The toilet flushing device as claimed in claim7, wherein the container for toilet flushing water is partially enclosedby two elastic membranes and partially by a rigid wall between the twomembranes.
 11. A toilet-flushing device, comprising: a container fortoilet flushing water; wherein the container is partially enclosed by anelastic membrane and partially by a rigid wall that has an unrestrictedconnection to a source of water under pressure that is sufficient toextend the membrane and an outlet in the rigid wall for the flushingvalve operable to release water from the container for a flush of atoilet bowl or urinal, and the inlet for water under pressure is aspiggot that is always open, save for a non-return valve fitted toprevent backflow into the supply pipes; and a flushing valve connectedto the flushing outlet of the container, which valve comprises a valveseat, a diaphragm including a plug that can seat on the valve seat, awall joining with the diaphragm to enclose a space within the diaphragmand the wall, an aperture in the plug upstream of the valve seat, and acontrol aperture in the wall downstream of the seat, that can be closedand opened by a control means operable by a user of the toilet-flushingdevice.
 12. The toilet flushing device as claimed in claim 11, wherein aconnection from the space above the diaphragm that is enclosed to a trapis provided, so that when the flushing valve is opened and the membranerelaxes, it draws air from the trap into the space above the membraneand reduces the pressure in the trap and enhances the rate of flush intothe trap.
 13. The toilet flushing device as claimed in claim 11, whereinthe container for toilet flushing water is partially enclosed by twoelastic membranes and partially by a rigid wall between the twomembranes.
 14. A toilet-flushing device comprising; a container fortoilet flushing water; wherein the container is partially enclosed by anelastic membrane and partially by a rigid wall that has an unrestrictedconnection to a source of water under pressure that is sufficient toextend the membrane and an outlet in the rigid wall for the flushingvalve operable to release water from the container for a flush of atoilet bowl or urinal, and a flushing valve connected to the flushingoutlet of the container, which valve comprises a valve seat, a diaphragmincluding a plug that can seat on the valve seat, a wall joining withthe diaphragm to enclose a space within the diaphragm and the wall, anaperture in the plug upstream of the valve seat, and a control aperturein the wall downstream of the seat, that can be closed and opened by acontrol means operable by a user of the toilet-flushing device; whereina connection from a space above the membrane that is enclosed to a isprovided, so that when the flushing valve is opened and the membranerelaxes, air is drawn from the trap into the space above the membraneand reduces the pressure in the trap and enhances the rate of flush intothe trap.
 15. A toilet-flushing device, comprising: a container fortoilet flushing water; and wherein the container is partially enclosedby two elastic membranes and partially by a rigid wall between the twomembranes that has an unrestricted connection to a source of water underpressure that is sufficient to extend the membrane and an outlet in therigid wall for the flushing valve operable to release water from thecontainer for a flush of a toilet bowl or urinal; and a flushing valveconnected to the flushing outlet of the container, which valve comprisesa valve seat, a diaphragm including a plug that can seat on the valveseat, a wall joining with the diaphragm to enclose a space within thediaphragm and the wall, an aperture in the plug upstream of the valveseat, and a control aperture in the wall downstream of the seat, thatcan be closed and opened by a control means operable by a user of thetoilet-flushing device; wherein a connection from a space above themembrane that is enclosed to a trap is provided, so that when theflushing valve is opened and the membrane relaxes, air is drawn from thetrap into the space above the membrane and reduces the pressure in thetrap and enhances the rate of flush into the trap.